Bleed the clutch system if filling the reservoir did not work. Since the system is hydraulic, air bubbles in the line can negatively affect clutch performance. Use a purge kit to do it yourself. Simply fill the tank with clutch fluid, pressurize it, open the bleed valve located on the cylinder near the left side of the engine compartment near the firewall, and insert the tank hose. The pressure from the bleed kit tank expels the old clutch fluid and replaces it with new fluid.